The present invention relates to bioerodible, sustained release intraocular implants and methods for treating an ocular disease or condition. Brimonidine (5-bromo-6-(2-imidazolidinylideneamino)quinoxaline) is an alpha-2-selective adrenergic receptor agonist effective for treating open-angle glaucoma by decreasing aqueous humor production and increasing uveoscleral outflow. Brimonidine is available in at least two chemical forms, brimonidine tartrate and brimonidine free base. Topical ocular brimonidine tartrate formulation, 0.15% Alphagan P® (Allergan, Irvine, Calif.), has been used to treat of open-angle glaucoma. The solubility of brimonidine tartrate in water is 34 mg/mL, while the solubility of brimonidine freebase is negligible in water. Topical formulations of brimonidine to treat glaucoma are administered daily. Hence, it would be advantageous to have a sustained release formulation of an alpha-2-selective adrenergic receptor agonist, such as brimonidine, which can be administered (i.e. by intrascleral injection or implantation of a suitable implant) once every one to six months to provide regular dosing of the alpha-2-selective adrenergic receptor agonist therapeutic agent to the eye of a patient in need thereof to thereby treat an ocular condition such as the elevated intraocular pressure characteristic of glaucoma.
Recent studies have suggested that brimonidine can also promote survival of injured retinal ganglion nerve cells by activation of the alpha-2-adrenoceptor in the retina and/or optic nerve. For example, brimonidine can protect injured neurons from further damage in several models of ischemia and glaucoma. See e.g. U.S. Pat. Nos. 5,856,329; 6,194,415; 6,248,741, and; 6,465,464.
Glaucoma-induced retinal ganglion cell degeneration (neurodegeneration) is one of the leading causes of blindness. This indicates that brimonidine can be utilized in glaucoma management in which neuroprotection (through mitigation of neurodegeneration) and/or intraocular pressure reduction are valued outcomes of the therapeutic regimen. For brimonidine to protect the optic nerve, however, it must have access to the posterior segment of the eye at therapeutic levels. Hence, it would be advantageous to have a sustained release formulation of an alpha-2-selective adrenergic receptor agonist, such as brimonidine, which can be administered (i.e. by intravitreal injection or implantation of a suitable implant) once every one to six months to provide regular dosing of the alpha-2-selective adrenergic receptor agonist therapeutic agent to the eye of a patient in need thereof to thereby treat an ocular condition such as neurodegeneration another retinal disorder or condition such as macular degeneration, macular edema or other retinopathy.
Macular degeneration, such as age related macular degeneration (“AMD”) is a leading cause of blindness in the world. It is estimated that thirteen million Americans have evidence of macular degeneration. Macular degeneration results in a break down the macula, the light-sensitive part of the retina responsible for the sharp, direct vision needed to read or drive. Central vision is especially affected. Macular degeneration is diagnosed as either dry (atrophic) or wet (exudative). The dry form of macular degeneration is more common than the wet form of macular degeneration, with about 90% of AMD patients being diagnosed with dry AMD. The wet form of the disease usually leads to more serious vision loss. Macular degeneration can produce a slow or sudden painless loss of vision. The cause of macular degeneration is not clear. The dry form of AMD may result from the aging and thinning of macular tissues, depositing of pigment in the macula, or a combination of the two processes. With wet AMD, new blood vessels grow beneath the retina and leak blood and fluid. This leakage causes retinal cells to die and creates blind spots in central vision.
Macular edema (“ME”) can result in a swelling of the macula. The edema is caused by fluid leaking from retinal blood vessels. Blood leaks out of the weak vessel walls into a very small area of the macula which is rich in cones, the nerve endings that detect color and from which daytime vision depends. Blurring then occurs in the middle or just to the side of the central visual field. Visual loss can progress over a period of months. Retinal blood vessel obstruction, eye inflammation, and age-related macular degeneration have all been associated with macular edema. The macula may also be affected by swelling following cataract extraction. Symptoms of ME include blurred central vision, distorted vision, vision tinted pink and light sensitivity. Causes of ME can include retinal vein occlusion, macular degeneration, diabetic macular leakage, eye inflammation, idiopathic central serous chorioretinopathy, anterior or posterior uveitis, pars planitis, retinitis pigmentosa, radiation retinopathy, posterior vitreous detachment, epiretinal membrane formation, idiopathic juxtafoveal retinal telangiectasia, Nd:YAG capsulotomy or iridotomy. Some patients with ME may have a history of use of topical epinephrine or prostaglandin analogs for glaucoma. The first line of treatment for ME is typically anti-inflammatory drops topically applied.
Diabetic retinopathy is the leading cause of blindness among adults aged 20 to 74 years. Macular ischemia is a major cause of irreversible vision acuity loss and decreased contrast sensitivity in patients with diabetic retinopathy. The capillary nonperfusion and decreased capillary blood flow that is responsible for this ischemia is seen clinically on the fluorescein angiogram as an increase in the foveal avascular zone (FAZ) or an irregularity of the outline of the FAZ. These findings are predictors of the other, perhaps more well-known, sight-threatening complications of diabetic retinopathy, including macular edema and proliferative retinopathy. Perhaps more importantly, extensive capillary nonperfusion is also a predictor of a poor visual prognosis from diabetic retinopathy.
The exterior surface of the normal globe mammalian eye has a layer of tissue known as conjunctival epithelium, under which is a layer of tissue called Tenon's fascia (also called conjunctival stroma). The extent of the Tenon's fascia extending backwards across the globe forms a fascial sheath known as Tenon's capsule. Under Tenon's fascia is the episclera. Collectively, the conjunctival epithelium and the Tenon's fascia is referred to as the conjunctiva. As noted, under Tenon's fascia is the episclera, underneath which lies the sclera, followed by the choroid. Most of the lymphatic vessels and their associated drainage system, which is very efficient at removing therapeutic agents placed in their vicinity, is present in the conjunctiva of the eye.
A therapeutic agent can be administered to the eye to treat an ocular condition. For example the target tissue for an antihypertensive therapeutic agent to treat the elevated intraocular pressure characteristic of glaucoma can be the ciliary body and/or the trabecular meshwork. Unfortunately, administration of an ocular topical antihypertensive pharmaceutical in the form of eye drops can result in a rapid wash out of most if not all of the therapeutic agent before it reaches the ciliary body and/or the trabecular meshwork target tissue, thereby requiring frequent redosing to effectively treat a hypertensive condition. Additionally, side effects to patients from topical administration of antiglaucoma medications and their preservatives range from ocular discomfort to sight-threatening alterations of the ocular surface, including conjunctival hyperemia (eye redness), stinging, pain, decreased tear production and function, decreased tear film stability, superficial punctate keratitis, squamous cell metaplasia, and changes in cell morphology. These adverse effects of topical antiglaucoma eyedrops can interfere with the treatment of glaucoma by discouraging patient dosing compliance, and as well long-term treatment with eyedrops is associated with a higher failure of filtration surgery. Asbell P. A., et al Effects of topical antiglaucoma medications on the ocular surface, Ocul Surf 2005 January; 3(1):27-40; Mueller M., et al. Tear film break up time and Schirmer test after different antiglaucomatous medications, Invest Ophthalmol Vis Sci Mar. 15, 2000; 41(4):S283. Thus it would be advantageous to have an intraocular, sustained release formulation of an alpha-2 agonist for treating glaucoma which does not have the side effects rapid drug wash out, ocular discomfort, conjunctival hyperemia (eye redness), stinging, pain, decreased tear production and function, decreased tear film stability, superficial punctate keratitis, squamous cell metaplasia, and changes in cell morphology.
It is known to administer a drug depot to the posterior (i.e. near the macula) sub-Tenon space. See eg column 4 of U.S. Pat. No. 6,413,245. Additionally, it is known to administer a polylactic implant to the sub-tenon space or to a suprachoroidal location. See eg published U.S. Pat. No. 5,264,188 and published U.S. patent application 20050244463.
Drug delivery systems have been formulated with various active agents. For example, it is known to make 2-methoxyestradiol poly lactic acid polymer implants (as rods and wafers), intended for intraocular use, by a melt extrusion method. See eg published U.S. patent application 20050244471. Additionally, it is known to make brimonidine poly lactic acid polymer implants and microspheres intended for intraocular use. See eg published U.S. patent applications 20050244463 and 20050244506, and U.S. patent application Ser. No. 11/395,019. Furthermore, it is known to make bimatoprost containing polylactic acid polymer implants and microspheres intended for intraocular use. See eg published U.S. patent applications 2005 0244464 and 2006 0182781, and U.S. patent application Ser. Nos. 11/303,462, and; 11/371,118.
Brimonidine is an α2B-selective adrenergic agonist used to treat open-angle glaucoma by decreasing aqueous humor production and increasing uveoscleral outflow. The chemical structure of brimonidine tartrate is:

The chemical formula for brimonidine tartrate is F, 5-bromo-6-(2-imidazolidinylideneamino)quinoxaline tartrate C15H16N5O6Br or (C11H10BrN5.C4H6O6).
Brimonidine tartrate has been used in ophthalmic solutions in concentrations of 0.2%, 0.15% and 0.1%. It has been suggested that brimonidine can have a neuroprotective effect upon retinal cells. See eg U.S. Pat. Nos. 5,856,329; 6,194,415; 6,248,741, and; 6,465,464.
Biocompatible implants for placement in the eye have been disclosed in a number of patents, such as U.S. Pat. Nos. 4,521,210; 4,853,224; 4,997,652; 5,164,188; 5,443,505; 5,501,856; 5,766,242; 5,824,072; 5,869,079; 6,074,661; 6,331,313; 6,369,116; 6,066,675, and 6,699,493. Relevant U.S. patent applications include Ser. Nos. 10/020,541; 09/998,718; 10/836,911; 11/119,021; 11/394,765; 12/024,010; 12/024,014; 12/024,017; 10/837,143; 11/118,519; 11/927,613; 11/927,615; 11/395,019, and 11/565,917.
It would be advantageous to provide eye implantable drug delivery systems, such as intraocular implants, and methods of using such systems, that are capable of releasing a therapeutic agent at a sustained or controlled rate for extended periods of time and in amounts with few or no negative side effects to treat an ocular disease or condition such as glaucoma, neurodegeneration, or a retinal disorder or condition.